It is known that epoxide compounds containing more than one epoxide group in the molecule, also called polyepoxides, may be cured to infusible and insoluble products by means of curing agents such as polyfunctional amines. Such amine-cured products are well known to possess a number of favorable properties such as good strength, good adhesion, and limited shrinkage.
For some applications, however, the so produced amine-cured products do not have the desired degree of hardness. But what renders the amine curing agents particularly inconvenient is that they are very harmful physiologically and as liquid products have an undesirably high vapor pressures. Therefore, their practical application requires extensive precautionary measures.
In order to overcome this disadvantage and at the same time increase the curing rates, boron trifluoride complex compounds have been suggested as curing agents. The complex compounds of boron trifluoride with basic nitrogen-containing compounds such as ammonia, amines, piperidine, etc. are suitable curing agents for use at elevated temperatures. Boron trifluoride oxime complex compounds have been suggested as cold-setting curing agents. It is also known to use hexamethylenetetramine as reactant or activator in the preparation of epoxide polyadducts. Hexamethylenetetramine contains ammonia in latent form, which when occuring intermediarily readily volatilizes.
It is one object of this invention to provide a process using a curing agent having the favorable properties of the known amine curing agents but being physiologically inoffensive and being capable of curing or setting under any desired conditions, i.e. at any desired temperature. Another object is to provide a curing agent which is also suitable for use in mixtures of polyepoxides and compounds or resins reactive with formaldehyde. Still another object is to provide cured products having an improved degree of hardness and elasticity. Other objects will be apparent to those skilled-in-the-art.